Schematic designator

On Mon, Mar 18, 2024 at 10:16 PM Jay Hennigan via Jukebox-list < jukebox-list@lists.netlojix.com> wrote:

On 3/18/24 17:27, Jukebox Repairman via Jukebox-list wrote:

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The parts list shows it as CR5107

Is that the actual part number or the schematic designator? Seeburg part numbers are typically all numeric, usually six digits. I don't have the schematic for that to try to evaluate its function.

-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV

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Thanks Jay I’ll do that tomorrow.

Regards Rick

On Mon, Mar 18, 2024 at 10:59 PM Jay Hennigan via Jukebox-list < jukebox-list@lists.netlojix.com> wrote:

On 3/18/24 19:18, Jukebox Repairman via Jukebox-list wrote:

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Schematic designator

What's the actual Seeburg part number? Stabistors are essentially diodes with a well defined forward voltage drop. Is it a stereo amplifier and if so can you measure the voltage drop across the same part in the working channel?

Also if you can scan the schematic and post it to an image site that would help. imgur.com is a good one.

-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV

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On 3/20/24 22:19, Chan Gade via Jukebox-list wrote:

There is nothing special about it. Replace with two silicon diodes in series. If you measure them you'll see they equal two regular diodes in series (around 1200 ohms DC resistance).

According to the cross-reference that John Robertson posted earlier, it looks like a plain old silicon diode, not two in series.

Also, you can't really measure the DC resistance of a diode. Yes, it will show something on an ohmmeter when forward biased, but the reading is essentially meaningless. It will vary widely based on the design of the ohmmeter.

While at it, replace all the "stabistors" in the AGC circuit as well. They often fail resulting in unequal levels depending on the amount of gain reduction being used.

I'm not familiar with the SAMI, but there are indeed weird diodes in the AGC of other Seeburg amps that are equivalent to two silicon diodes in series.

In the Seeburg amps these are not being used as simple rectifiers.

For bias they are used as temp sensors. Using only one diode results in too little idle bias, though this can be adjusted in TSA6-on.

Beginning with TSA-7 they were used as active gain attenuation in the AGC. A single diode will result in too much attenuation for a given AGC voltage.

In the earlier amps using the packaged selenium (red and yellow cap) using three in series for each leg more closely replicates the attenuation ratio of the originals. I use only 2 there as well since it makes the AGC more effective. This brings the max. attenuation from only about 8 db up to about 12 db gain reduction.

FWIW: I add some R&C decoupling to the AGC amp transistors to boost the range to 19DB max which is similar to the tube units using 6SK7 and 6BJ6. The TSA amps are still slightly less effective at leveling due to a softer knee as compared to the harder tube type.

Regards, RobNYC On Thursday, March 21, 2024 at 12:40:54 AM GMT-5, Jay Hennigan via Jukebox-list jukebox-list@lists.netlojix.com wrote:

Rick, what's the voltage drop across the stabistor in the working channel? If it's around 0.7 volts, use a single silicon diode.